Human obesity represents a serious world-wide health problem. One consequence of obesity is the development of insulin resistance, hyperglycemia, and metabolic syndrome that can lead to cell dysfunction and type 2 diabetes. It is therefore important that we gain an understanding of the physiology and pathophysiology of the development of obesity because this knowledge represents a basis for the design of potential therapeutic interventions. A significant challenge to understanding diet-induced obesity is the complexity of the signal transduction pathways that mediate the response. Indeed, these signaling pathways function within an interacting network. Here we propose to employ a systems biology approach to understanding the response to feeding a high fat diet by combining physiological analysis together with quantitative analysis of the signal transduction networks and the genomic response. This analysis requires the coordinated collaborative efforts of several laboratories with complementary expertise together with robust data analysis and computational modeling. We will focus our analysis on the liver. The overall goal of this research program is to understand the mechanism of the hepatic response to diet-induced obesity. Achievement of the goals of this proposal will increase understanding of the molecular response to obesity. We anticipate that the successful completion of this research program will lead to the identification of nodes in the signaling network that may represent a basis for the design of novel therapeutic strategies for the treatment of metabolic syndrome and type II diabetes. The Specific Aims of this proposal are to: 1. Examine the hepatic response to feeding a high fat diet. 2. Integrate data analysis using computational modeling. 3. Test predictions obtained from computational modeling.